What does the .= operator mean in PHP?

Question

I have a variable that is being defined as

$var .= "value";

How does the use of the dot equal function?

Solution 1

It's the concatenating assignment operator. It works similarly to:

$var = $var . "value";

$x .= differs from $x = $x . in that the former is in-place, but the latter re-assigns $x.

Solution 2

This is for concatenation

$var  = "test";
$var .= "value";

echo $var; // this will give you testvalue

Solution 3

the "." operator is the string concatenation operator. and ".=" will concatenate strings.

Example:

$var = 1;
$var .= 20;

This is same as:

$var = 1 . 20;

the ".=" operator is a string operator, it first converts the values to strings; and since "." means concatenate / append, the result is the string "120".

Comments

[Deadlock]

Used to append value in variable which already contains some value...

[Marc Baumbach]

+1 I'm not sure why there was a down vote either. This is also backed by php.net/manual/en/language.operators.string.php

[m93a]

Both do re-assign $x.

[Blender]

@m93a: Can you link to documentation?

[m93a]

@Blender OK, you're right, they don't. The $x .= performs ~2 times faster than $x = $x . but the spec isn't really verbose on this matter.

[Radmation]

yes but only for strings - i just spent fuc*** hours wondering why the hell my float was getting turned into a freaking string! Apparently this damn operator will cast your damn floats to strings.. I am so annoyed right now!

[Camille Goudeseune]

Do you mean that $x = "Hi"; $pi = 3.14; $x .= $pi; changes $pi?!